1. Field of the Invention
This invention relates to a miniature push-button switch, and more particularly to a miniature push-button switch having an improved switch body.
2. Description of the Prior Art
Recently, there has been a highly increased demand for developing a miniature push-button switch having dimensions as small as, for example, 8 mm in diameter and 25 mm in length with the miniaturization of electrical and electronic equipments. A typical one of such miniature push-button switches is adapted to carry out the switching operation by moving a movable contact which is provided to slidingly contact fixed contacts. The fixed contacts of the miniature push-button switch of such construction generally comprise a normally closed fixed contact (hereinafter referred to as "NC fixed contact"), a common fixed contact (hereinafter referred to as "C fixed contact") and a normally opened fixed contact (hereinafter referred to as "NO fixed contact") which are arranged in order along the sliding direction of the movable contact. Also, the miniature push-button switch is constructed to include switch terminals comprising a normally closed switch terminal (hereinafter referred to as "NC switch terminal"), a normally opened switch terminal (hereinafter referred to as "NO switch terminal") and a common switch terminal (hereinafter referred to as "C switch terminal") interposed between the NC switch terminal and the NO switch terminal which are arranged to project from a switch body.
The miniature push-button switch of such construction currently used in the art is generally divided into two types. One is the type where a movable contact id slidingly moved through a switching element to electrically connect a C fixed contact and an NO fixed contact with each other through the movable contact, to thereby carry out the operation of the switch. The other is the type where the electrical connection between a C fixed contact and an NC fixed contact is accomplished without utilizing the operation of a switching element. The former type is highly predominantly used in the art.
The miniature push-button switch of the former type will be described hereinafter.
As such a miniature push-button switch, two kinds of push-button switches as shown in FIGS. 1 and 2 have been proposed and used in the art. The push-button switch shown in FIG. 1 is adapted to carry out the switching operation by means of a movable contact 221 of a clip-like shape fitted at the base portion thereof in a recess 227 formed at one side of a switching element 220 and a plurality of fixed contacts 215A, 216A and 217A. In the push-button switch of such construction, when a push button 240 is downwardly pushed, the movable contact 221 is slidingly moved while interposing the fixed contacts 215A and 216A between the contact surfaces thereof, establishing the electrical connection between the central C fixed contact 216A and the lower NO fixed contact 217A. When the push button 240 is released from the downward pressing, the switching element 220 is upwardly moved by means of the upward force of a compression coiled spring 245 interposed between a recess 228 formed at the lower surface of the switching element 220 and a sliding element 229 to allow the movable contact 221 to be upwardly moved, so that the switch is returned to the original position shown in FIG. 1.
The miniature push-button switch shown in FIG. 2 is constructed in a manner such that a projection 275 of a switching element 270 acting as the center of the pivotal movement is positioned on a receiver member (not shown) provided on a switch body 260, a movable contact 271 of a clip-like shape is securely fitted in a recess formed at the front half 270A of the switching element 270, a compression coiled spring 295 acting to upwardly force a push button 291 is positioned at one end thereof on the rear half of the switching element 270, and a plate-like operating element 279 downward extending from the lower end surface of the push button 270 is engaged with the rear half of the switching element 270. In the push-button switch of such construction, when the push button 291 is pushed for the switching operation; the switching element 270 is tilted in the left direction in FIG. 2 against the force of the compression coiled spring 295 to carry out the electrical connection between an NO fixed contact 267A on the left side and a central C fixed contact 266A through the movable contact 271. When the push button 291 is upward released; the electrical connection between the central C fixed contact and an NC fixed contact 265A on the right side is carried out through the movable contact 271 by means of the upward force of the compression coiled spring 295, so that the push-button switch is returned to the original position shown in FIG. 2.
As can be seen from the foregoing, the conventional push-button switches shown in FIGS. 1 and 2 each are constructed in the manner that the C fixed contact is arranged at the central portion of the switch, resulting in a C switch terminal being arranged between an NO switch terminal and an NC switch terminal. However, as described above, the recent miniaturization of electrical and electronic equipments requires switches to be highly miniaturized to a degree sufficient to cause the interval between the switch terminals to be as small as, for example, about 2.5 mm. This renders the soldering operation for wiring carried out with respect to the C switch terminal positioned at the central portion of the switch and the NO switch terminal arranged adjacent thereto highly troublesome and difficult. Also, this causes the switch terminals to be loosened or damaged by soldering heat, resulting in the switching operation often being impossible due to contact failure. Furthermore, in the conventional switch shown in FIG. 1, the switch terminals are arranged in the direction perpendicular to that of operating the push button. This necessarily results in the width of the switch being significantly large, to thereby cause the switch to be large-sized. Accordingly, it would be highly desirable to develop a push-button switch significantly miniaturized corresponding to the recent miniaturization of electrical and electronic equipments and operated with good reliablity.